The Stovebolt Site Forums The Shop Area The Electrical Bay Reproduction Ignition Switch Goofy Symptoms

1949 3600 235 SM420

I just replaced the sloppy universal ignition switch in my 3600 with a reproduction switch and bracket. It's a bit of an effort getting that assembly in! Anyway, the new switch isn't passing power to anything. I wired it as standard, with the top lug taking power from the ammeter and the bottom left lug connecting all the power out lines, and the third lug (right) not doing anything. With the key off, I read battery voltage (13v) at the top lug, and no voltage at either of the other two lugs (just digital meter millivolts). With the key on, I lose the 13v at the top lug, and all three lugs display wandering, transient millivolts readings of no consequence. With the key on, nothing lights up, no fuel gauge, etc.

Is this just symptomatic of a bad reproduction part? Or is there something else I can check?

EDIT: minor update, I just took the switch out of the mounting bracket so it's dangling from its wires and not touching anything, and now it consistently shows voltage where it should be: battery voltage at the top terminal and when the key is on I get battery voltage at the top terminal and the bottom left terminal. I'm guessing that the switch is grounding somehow to the mounting bracket and must be a faulty part.

It could be a poor quality part and as you tighten the outer nut it could be causing the switch to deform and disrupt the contacts?

You need to do some simple testing before you know what is wrong. My reaction is not distortion or bad switch, but testing should give a clue.

1. Test the switch with no wires attached. I.E. Test for continuity (non voltage test). Should read: sw off= no continuity between any terminal to another and no continuity between any terminal and sw case.

Sw on= continuity to any two terminals but no continuity between any terminal and sw case.

2. Please provide switch and bracket part numbers and vendor. Provide pix of switch mounted to bracket.

3. "(just digital meter millivolts)". If you applied battery voltage to a terminal and are reading the other terminals, you are reading battery voltage not "meter voltage". Explain the tests you did..... where were black and red probes touching when you got only "millivolts" and where were they touching when you got normal results. Also, What mode was meter set to?

4. Please carefully answer all questions and report test results before doing anything else. Wait for next tests.

Some of the universal switches were made for magneto powered machinery. It shorts the ign. to ground when turned off.

This is something I ran into last summer while testing the new ignition switch before wiring. Bad manufacturing. With key off and key out it passed voltage. With ignition on it opened the circuit not passing voltage. Contacted who I ordered it from and they sent a replacement for free not wanting the first one back. I thought that was odd, being they are $50-70 depending on where you get it. The replacement one did the exact same thing. I tore apart the old original switch to see how it was constructed, and not wanting to wait for another resolve, I tore the new one open. The center plastic disk was manufactured the opposite of original. I drilled new holes for the springs and re-assembled. Works great. I verified the with the switch in, the mount would be grounding for the bulb to work, and it didn’t ground out the switch terminals. But it wasn’t something I checked before tear down. It is just a 2 position off/on switch. You may have a poorly made switch also.

Hi Bartamos, when the key is off the Ohm meter shows no continuity to either post or switch casing from the "Battery" post (which actually connects the battery voltage via the Ammeter). When the key is on, there is perfect continuity between "Battery" and either of the two accessory posts (shows 0 ohms and I get the continuity tone from the multimeter). With the key on, from "Battery" to the case the ohmmeter shows 0.L ohms, and does not give the continuity tone.

My coil/points are powered directly from the key (internal resistor, no wire from the starter), is it possible that with the key on the power draw from the coil is depressing the voltage? Sometimes I get full battery voltage on the accessory post (with key on) and sometimes not.

A pic of the switch is below, next time I put it in the dash I'll snap a pic of that. The mounting posts sit really close to a lot of groundable material. I think I bought this from Classic Parts, but it could have been any of the other vendors.

Edit: I put the reproduction switch back in (dangling, not in the panel) and this time when I turned the key to on the switch made a "shorting/arcing" sound and I saw the fuel gauge go dead. Not enough of a short to smoke or spark but you could hear it. Turned the switch off and back on and it did it again, then went dead (the fuel gauge and radio) permanently. The switch still tests fine on the bench: continuity where it's supposed to be and no shorting to the case of the switch.

When the engine turns over, I don't get 12 volts at any of the terminals on the back of the switch. I would think the voltage would stay at battery voltage even when turning over, no?

Unless the ignition switch is marked, there is no "Battery terminal". You can use any of the terminals for that. There is no acc position. I believe you have almost proven that. That was part of the reason for the test. I believe switch is all terminals on and all terminals off.

OK so to get a visual in my mind and to suggest further.
1. Don't put switch back, leave it off and disconnected. Always use the new switch.
2. Test continuity and no continuity between the "other two" to each other and report. You missed the "any two" test. I'm trying to eliminate or include the switch as the problem as the very first step.
3. Don't hook anything up or test anything while I'm trying to get on a roll. You also missed that request and have possilbly blown components.
4. Do you have foot start or a solenoid?
5. Can you please describe in detail where each wire to or from ignition switch terminals go. I'm trying to get a visual of your electrical and at the same time do what I would do if I was there. Not trying to be big boss man but you have tried and were getting nowhere and asked for help so let me try with your hands and reports. If that method is not suitable I will understand.
6. Is ign sw bracket hard to get off?
7. Do you have an internally resisted coil and no ballast resistor? Is the coil 12V? Is there no bypass circuit? You asked "When the engine turns over, I don't get 12 volts at any of the terminals on the back of the switch. I would think the voltage would stay at battery voltage even when turning over, no?" The starter can rob the coil of voltage, that is what a bypass circuit is for.

I have further tests/plans but I do one step at a time. Some of your ideas/guesses are valid but I'm not considering anything yet.
Can you number your answers per question numbers?
Remember don't do or change anything or do tests via energizing circuits. I will get back after I see your response. Disconnect neg bat cable until we synergize.

Hi Bartamos. No worries about all the steps. These things are tough to diagnose via the internet.

Here's the answers:

Yes it is just an on/off switch. So when off, there is no continuity between any terminal to any other terminal (tested all possible combinations of the 3 terminals) nor is there continuity to the case of the switch. I call the power in terminal "Battery" just out of habit, none of these three terminals are labeled.

With the switch on there is continuity to all three terminals, or of course between any two terminals, and there is no continuity to the case.

Truck has the foot starter, no solenoid. Coil is 12V with internal resistor, no external ballast resistor on the firewall or in the circuit. There is no bypass circuit to the coil.

The ignition switch bracket is not hard to get off.

Wires to the ignition switch:
1. Power IN from the Ammeter, this goes on it's own terminal (the one I was habitually calling "Battery")
2. Power OUT to the coil
3. Power OUT to the gauges
4. Power OUT to the heater fan
5. Power OUT to the radio

The Power out wires go on any lug other than the one for Power IN

Battery is 3 years old, and seems to hold good voltage (13V on the multimeter when fully charged on the bench)

1. Make a jumper wire from a battery source, not the ammeter, with a 12V 5A inline fuse. No switch involved.
2. Attach it one at a time to an "out" wire. Not several at once.
3. Start with gauges, then the coil to see 12V at positve coil terminal, then heater, then radio.
4. Do you have a fuse panel or any fuses? if so where are they located and what to the protect?
5. New harness? Part no?...... or old original wiring?....or previous owner bird nesting?

After you report findings, we can discuss adding a bypass circuit.

Of course be real carful not to touch the jumper to anything or a ground, just the wire being tested.

Original wiring, and it's lived a rough life ;-) No bird or mouse nesting, but the original insulation.

Fuses: just the original fuse panel on the firewall, only a handful of fuses in there for lights and such.

Will report back after making the jumper wire with fuse.

"Original wiring, and it's lived a rough life ;-) No bird or mouse nesting, but the original insulation."

That can definately be a problem. that's why the 5A fuse. I mention doing the heater and radio last becasue they may blow a 5A.

IMPORTANT: do electrical gauges (gas is the only electrical gauge) have voltage reducers? Does the heater or radio have reducers or are they 12V?
Be careful not to bypass a voltage reducer when doing the jumper test.

Also, you are not using a meter for this test except for the coil pos terminal. You are seeing if the components function.
Make sure you turn the heater and radio switches on when testing those.

"Bird Nest" wiring refers to under dash scrambled up mess of wires: added wires, butt spliced wires, old disconnected wires, inline fuses, twisted together connections with loose electrical tape and so on.

Myself and others had a conversation about your wiring back in Feb 2021. probably time to get a harness put in. I enjoy helping and recommending with that. I see you are plenty capable to do that with a little help. We will talk about that later if you wish, by email, because it's a lot of back and forth.

So with the 5A jumper connected to each wire one at a time we get:

Fuel gauge works
Radio works
Heater fan works
Coil shows 12.3V at the positive terminal (grounding the multimeter at the head)

Battery tested as good at O'Reilly's

I don't know about voltage dropping resistors in line anywhere but will go looking for them. I assume that a 1949 truck started life as a 6 volt?

I suppose the next thing to test is the wiring coming from the Ammeter that powers the key switch?

Stand by for message

Yes your truck came as 6V. Gas gauge must either be 12V or has a reducer because it works. Same with heater and radio.
Do you have a generator and voltage regulator or an alternator?

Your previous test show you had 12V incoming and outgoing with switch dangling and NO BRACKET. So this time use 5A jumper as input, NOT ammeter, rig it like that one more time. dangling, no bkt. All outgoing wires permanently hooked up to switch.
Turn switch on and see if everything works and coil gets 12V. No meter measureing other than that.

you need to buy a 12V ice pick style volt tester.

This system has a generator and voltage regulator. Generator age is unknown, voltage regulator is 2 years old.

Does the voltage reg say 12V?

Are you going to do the retest now? i only ask becasue I'm leaving for awhile. No hurry on my part.

Had you been driving around for a period of time, happy go lucky, before all this happened???????

I'm Back!

Connected the 12g 5A jumper to the key switch and the Coil Out wire. It shows 12.3V at the + terminal of the coil.

Prior to this, the truck had been a reliable starter and was my regular work truck. However the generic key switch had a history of working lose and grounding itself (2 times over the last year) so I had ordered this reproduction switch (a long time ago) with the goal of solving that once and for all. Truck was sitting over Christmas for 3 weeks, battery got too low to start so I charged it and changed out the key switch.

Which terminal on the Voltage Regulator is supposed to read 12V?

You are supposed to hook up ALL "out" wires, using jumper input, to dangling switch, no bracket and see if gauge, coil, heater and radio still work as they did with previous test with no switch. Good result? all systems go?

Now same test with bracket attached and dangling. We know that any combination of switch terminals will work, so use the terminals on switch that are farthest from bracket metal when switch mounted to bkt. Arange the wire exit routing accordingly. Use all three if that is better. Good result? please post good, clear, well lit pics of that setup, Showing the out wires and their terminal ends screwed to the switch while switch is on bracket

I am asking if the voltage regulator is marked "12V" on it, not to test it.

The Voltage Regulator is marked 12V

With ALL the Power Out wires hooked up, and switch dangling, there is a slight voltage drop from the Battery itself to the switch terminals (12.5V at the Battery, 12.2V at the terminals). The Gauges work and the Radio works. Turning on the Fan (original option Fan and showing its age) causes the 5A jumper fuse to blow. There's also 12.2V at the + terminal of the Coil.

I haven't attached the bracket and dangled the whole assembly yet. Will do so in 1 hour (11 a.m. Pacific time).

Edit: Same outcome with the bracket attached and dangling: Guages and Radio work, 12.2V at the Coil. Did not try the fan, but it has volts too. No continuity registering between terminals and any ground. With the bracket attached out of the truck, the mounting screws (that mount the bracket to the truck) extend far enough to touch the switch case now, but no matter, there is no grounding/continuity between any terminal and the switch case or the bracket. This is all using the 5A Jumper wire from the battery.

Edit: So with the dangly switch wired with all the Accessories and the 5A Jumper, the Accessories (Guages, Radio, Fan) all show power and operate (although the Fan draws more than 5A and will blow the inline Jumper fuse) and the coil gets 12.2V.

With the dangly switch wired the same, but with the power coming from the Ammeter line in the Truck (so no 5A Jumper connection), I can read 12.3V on the Power In terminal, but when I turn the key on none of the Accessories show signs of life. So everything the same, but switch from the 5A Jumper and no amps, just volts.

Be careful, very strange the heater worked on the one at a time test with 5A jumper. but thru switch with 5A jumper it blew fuse.
Was the heater wire hooked to a separate switch terminal; or same terminal as the other outs?

It could be as you say, the old motor, if bad bearings/bushing or fan blade interference, it will put a drag on the motor and draw more amps possibly. This would be an intermittent happening. So we will ignore that for today.

I'd guess that the Heater on High, plus the coil, radio and gauges was just enough to go over 5A.

But the big thing is that the Jumper will provide power to the switch (and on to the Accessories), but the line from the Ammeter won't. That line will read voltage (12.2/3) when connected to its switch terminal, but turn the key and nothing comes to life (not even the fuel gauge). So looks like a bad line there.

OK good news. So all seems to be "able" to work. So you need to "enable" your truck with a new, universal, prewired fuse panel harness.Example

At that time, I recommend installing a bypass system, alternator and take heater motor out and refurbish. i can kelp with all that. Step by step. Without new harness and all the fuses it supplies, you will have ongoing issues I'm afraid.

Sure, but no point doing all that work in the street. It's probably better to run a new power wire to the switch for now so I can get it moving and into the driveway for doing something that involved.

The 12V Jumper comes straight from the battery positive post.

Since all of the "Outs" are working, it makes sense to check the "Ins." The 12V/5A Jumper is working, so take that off, test the existing power in from the Ammeter for voltage (yes, 12.2-3V), connect it to the switch (still 12.2V) and see if it delivers voltage across the switch to the accessories (no it does not). So enough continuity to read voltage but not deliver amps.

So the line from the Ammeter to the Key Switch is now suspect, or it could be further up the line (Battery/Starter Terminal to Ammeter)

Just read your latest post, did you just now use the ammeter input with all outs connected to dangling switch on the bracket? That was not part of the plan so far. No ammeter hookup was advised yet. We can test that now if you want, I will advise how.

By the way, where did you tap into 12V with the jumper?

Use your cell phone to take pics of back of ammeter and the wire to switch to notice loose connections or routing/shorting issues.

Yes, need to move truck, it will start with just 5A jumper as input. Don't need ammeter to move truck.

FYI: According to 1949 wiring diagram, your ammeter output goes to:
1. headlight switch
2. Ignition switch
3. Voltage regulator

The voltage to the switch from the ammeter is 12V.... the voltage to the switch from jumper is 12V. The voltage to the ammeter comes from the battery post to the starter stud and on to, and straight thru, the ammeter. It must be that just a few strands of the old wire are still connected and voltage breaks down under load. Don't know. See part in green and proceed with what you think needs done there. Ammeters have a bad wiring idea, they do provide info. Voltmeter is a better wiring idea and supported by harness makers, same info, albeit not original.

It could possibly be a waste of time to find out what's wrong, if anything. with ammeter input/output if you are just moving truck to rewire location. We have proven the switch is OK, we have proven the accessories are OK....we have proven the wiring is not........ and the 12V conversion is not optimum.

Nothing loose or out of place on the back of the Ammeter and Gauge cluster, however the power supply wire from the Ammeter to the Ignition Switch is frayed where it goes up and over the steering column (about as inaccessible as possible ;-P ) and feels like it's broken quite a few strands (it's too "floppy" for such a heavy gauge). The strands that are visible are oxidized. I can't see any marks from arcing anywhere.

You probably found the problem. We kind of eliminated everything else.....maybe.
If you are not going to drive it anymore, just jumper the coil with a quick release method. If going to drive to work, bypass ammeter and rig a new 12V to switch. It will all get worked out when cluster removed/dropped at new harness install.

The harness install time effort depends on your time availability. A few days to a few weeks. It's a careful rip out of the old in a manner that keeps it in a "harness" configuration if possible for reference, save EVERYTHING. Then mount fuse panel inside firewall, probably upper left of left foot. Harness will have three basic harnesses, 1)front lights/engine....2)dash/dome and 3)rear tail/stop. If you have a turn signal switch on column, that's a separate easy effort.

It's your truck, so do what you think is best. I'm just giving my too sense. Let me know before buying something.
your generator is either a genuine 12V gen, a converted 6V or a 6V with a 12V reg.

I do have the added turn signals and extra Mickey Mouse ear tail lights and front lights. When I do the harness I'd like to delete those and put the flashers in the original tail lights.

I will replace the bad wire for the moment, but a whole new harness has been on the to-do list for a while. Did not know you could have a 6V generator with a 12V regulator.

Anything you want regarding lights is very doable. Including using "original" park or tail lights with dual filament sockets/bulbs. It's all available in the aftermarket.

Replacing the ammeter wire is a bandaid, but will be OK until some other old shredded wire gets bumped around and etc. It's more troublesome on old vehicles with limited fusing. In your case, all the lights are fused and the headlight switch should have a fuse and thermal overload resetting breaker. It's just you never know, after all the previous owners, what is lurking.

There have been folks using 6V gen with 12V reg. The gen will run up to possibly 30 volts if not regulated or "run away"..... so they just let it go to 12V. Tractor guys and others have done it with no problem. Members here use their 6V starters on 12V. A motor is sort of the opposite of a generator but same type components. One drives, the other is driven. I've never done it and don't recommend a 6V gen with 12V reg. Was just mentioned as the third possibility.
I did buy a 46 CJ2a VEC with that setup and it worked for the previous owner for a long time, but I changed to alternator.